Lanark, IL Weather & Growing Conditions
This Afternoon
78°F
Showers And Thunderstorms Likely
Showers and thunderstorms likely. Mostly cloudy, with a high near 78. South wind 5 to 10 mph. Chance of precipitation is 70%. New rainfall amounts between a half and three quarters of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 78°F | Showers And Thunderstorms Likely | 5 to 10 mph S | 69% |
| Tonight | 62°F | Showers And Thunderstorms | 5 to 10 mph NW | 90% |
| Sunday | 68°F | Rain Showers Likely | 10 to 15 mph NE | 55% |
| Sunday Night | 55°F | Chance Rain Showers | 15 to 20 mph NE | 34% |
| Monday | 64°F | Chance Rain Showers | 15 mph NE | 46% |
| Monday Night | 49°F | Chance Rain Showers | 10 to 15 mph NE | 26% |
| Tuesday | 63°F | Slight Chance Rain Showers then Partly Sunny | 15 mph NE | 18% |
| Tuesday Night | 47°F | Partly Cloudy | 5 to 15 mph NE | 7% |
| Wednesday | 66°F | Mostly Sunny | 10 mph NE | 2% |
| Wednesday Night | 50°F | Partly Cloudy | 5 to 10 mph NE | 1% |
| Thursday | 67°F | Mostly Sunny | 5 mph NE | 4% |
| Thursday Night | 51°F | Partly Cloudy | 0 to 5 mph NE | 4% |
| Friday | 70°F | Mostly Sunny | 5 mph NE | 3% |
| Friday Night | 51°F | Partly Cloudy | 5 mph E | 3% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Lanark, IL
Last spring frost
May 2
First fall frost
Oct 7
Growing season
154 days
Hardiness zone
5a
Explore more for Lanark, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Mt Carroll, Il (8.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.